This part of ISO/IEC 10026: a) provides a general introduction to the concepts and mechanisms defined in ISO/IEC 10026; b) defines a model of transaction processing; c) defines the requirements to be met by the OSI TP Service; and d) takes into consideration the need to coexist with other Application Services Elements, e.g. RDA (Remote Database Access), ROSE (Remote Operations Service Element) and non-ROSE based applications.